Microfiltration sterile filtration

Among the methods of field-based separations, membrane filtration is one of the most representative, which includes microfiltration, sterile filtration and ultrafiltration. Microfiltration is used for clarification and sterile filtration, and ultrafiltration for protein concentration and buffer exchange. ... 

Downstream Processing Microfiltration plays a significant role in downstream processing of fermentation products in the pharmaceutical and bioprocessing industry. Examples are clarification of fermentation broths, sterile filtration, cell recycle in continuous fermentation, harvesting mammahan cells, cell washing, mycelia recovery, lysate recovery, enzyme purification, vaccines, and so forth. 

The primary market for the disposable cartridge is sterile filtration for the pharmaceutical industry and final point-of-use polishing of ultrapure water for the microelectronics industry. Both industries require very high-quality, particle-free water. The cost of microfiltration compared to the value of the products is small so these markets have driven the microfiltration industry for the past 15 years. 

The u% of synthetic polymeric membranes for water purification is now an established technoli. Historically, this developn nt dates to the beginning of this century, when Zsigmondy and Bachmann prepared the first microporous membrane from cellulose esters. SimOar microfiltration membranes are now widely used in applications ranging fiom sterile filtration to fine particle removal. 

Table 12 shows the typical LRV values obtained using a polymeric and ceramic microfilter. Sterile filtration requires 100% bacteria retention by the membrane, whereas in many industrial bacteria removal applications the presence of a small quantity of bacteria in the filtrate may be acceptable. For example, drinking water obtained by microfiltration may contain nominal counts of bacteria in the filtrate which is then treated with a disinfectant such as chlorine or ozone. The use of ceramic filters may allow the user to combine the sterile filtration with steam sterilization in a single operation. This process can be repeated many times without changing filters due to their long service life (5 years or longer). 

Although it might seem reasonable to consider microfiltration and tighter filtration as sterile and an alternative to conventional sterile filtration, this temptation should be avoided. Because it is not presently possible to test the membrane s integrity, it is impossible to know if larger pores or microscopic tears are present. In fact, we have observed the use of ultrafilters in a sterile filtration application where Zygosaccharomyces present in the permeate at >10 GFU/mL. 

Microfiltration Symmetric microporous membrane, 0.1 to 10 pA pore radius Hydrostatic pressure difference, 0.1 to Ibar Sieving mechanism due to pore radius and adsorption Sterile filtration clarification... 

The microalgae are cultured in bioreactors under solar or artiflcial light in the presence of carbon dioxide and salts. The bioreactors may be closed systems made of polyethylene sleeves rather than open pools. Optimal conditions for pigment production are low to medium light intensity and medium temperatures (20 to 30°C). Pigment extraction is achieved by cell breakage, extraction into water or buffered solution, and centrifugation to separate out the filtrate. The filtrate may then be partly purified and sterilized by microfiltration and spray dried or lyophilized. 

The advantages and disadvantages of in-line microfiltration and cross-flow filtration are compared in Table 7.2. In general, in-line filtration is preferred as a polishing operation for already clean solutions, for example, to sterilize water... 

Microfiltration is a technique that allows the differential concentration in the retentate of the feed components that are larger than the average pore diameter of the membrane [8]. Developed as early as 1929 by Sartorius-Werke, in Germany, microfiltration is one of the oldest filtration technologies whose main use was for water and beverage sterilization [9,10]. MF membranes have pore diameter ranging 0.1-10 p.m, which can selectively separate particles with molecular weights >200 kDa based on sieve effect [8,11,12]. 

In the past ten to fifteen years or so, the applications sphere of cross-flow filtration has been extended to include microfiltration (MF) which primarily deals with the filtration of colloidal or particulate suspensions with size ranging from 0.02 to about 10 microns. Microfiltration applications are rapidly developing and range from sterile water production to clarification of beverages and fermentation products and concentration of cell mass, yeast, E-coli and other media in biotechnology related applications. 

All types of tangential microfiltration produce higher quality clarification than those achieved by filtration through a kieselguhr precoat. However, the filtrates are not always sterile, particularly when unclogging by reversed flow has destroyed the polarization layer. 

Membranes and separation cJiaracteristics in mlcroflltration Whereas filter clotbs/woven fabrics are useful for filtration of larger particles, microfiltration membranes are widely used in deadend filtration mode to remove effectively suspended matter in the size range 0.1 to 10 pm. The objective can be purification, clarification, sterilization, concentration and analysis. The suspended particle capture/retention efficiency Et may be described by... 

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